Our group is principally concerned with the molecular biology of HIV pathogenesis, particularly the pathogenesis of pediatric HIV disease. The course of HIV disease in pediatric patients differs substantially from the course of disease in adults. We are therefore particularly interested in trying to understand the involvement of host cell factors in HIV replication and the effect of HIV infection on the host cell. Our underlying hypothesis holds that there is one set of cellular conditions that is ideal for normal cellular growth and replication, that another set of conditions is ideal for viral replication, and that viruses (particularly HIV) have evolved ways of altering their host cells to enhance viral replication. During the past year, we have used cDNA microarray technology to begin to identify cellular genes with altered expression during HIV replication and to attribute the changes in cellular gene expression to particular stages of the viral replication cycle and individual viral gene products. As a proof-of-principal project we identified cellular genes that were differentially expressed in the presence of HTLV-1 Tax. We found that several genes were differentially expressed, including some that were previously identified and others that were not. Among the genes we found to be differentially regulated was the mixed lineage kinase MLK-3, which we showed mediates NF-kB signaling due to Tax, as was previously demonstrated for two other MAP3K kinases, MEKK and NIK. We also showed that the early HIV protein Nef, an HIV gene product dispensable for viral replication in vitro, but essential for a fully pathogenic virus, alters the expression of several cellular genes, including genes previously identified as playing a part in HIV replication. The results suggested that the expression of Nef helps to prepare the host cell for the subsequent stages of the viral replication We have also constructed small arrays containing the entire set of genes from several herpesviruses, including the Kaposi's sarcoma-associated herpesvirus (KSHV, or human herpesvirus 8, HHV-8). This technology was used to develop an initial description of the KSHV transcription program during the KSHV lytic replication cycle. The data delineate which viral genes are expressed at particular times during the viral replication cycle. It offers useful insights into viral replication and pathogenesis strategies and may help inform future approaches to the therapy for KS. Follow-on studies so far have shown that a KSHV-transformed primary effusion cell lines can be group into two different classes based on their biological and immunological properties and that the KSHV gene expression pattern also groups the cell lines into these same two classes, implying that the expression of the KSHV genes is responsible for the neoplastic phenotype. Another follow-on study showed that the KSHV K1 gene product, which contains an immunoreceptor tyrosine-based activation motif, can selectively suppress the expression of a subset of KSHV genes, suggesting that K1 may play a play in the maintenance of KSHV latency. We also collaborated on a study of the mechanism of action of a sulfur mustard, CEES, 2-chloroethylethyl sulfide. We showed that CEES downregulates the expression and phosphorylation state of the antiapoptotic protein Akt, while at the same time upregulating the expression of several caspases, suggesting that one mechanism through which this mustard agent kills cells is via the activation of cellular apoptotic pathways. We are also actively engaged in developing new therapies for pediatric HIV disease and in using newly available therapies to investigate key issues in pediatric HIV pathogenesis. This research is described with the pediatric HIV group in HAMB. It is 100% AIDS research. (About 20% of the work is also related to cancer.)